上載具有透明性的PNG圖像時出現問題？

Question

我在上傳具有透明性的PNG圖像時遇到了一些問題。

我將圖像上傳，裁剪並插入到數據庫中，當我嘗試在網站上顯示它們時，它們會變黑。 只有PNG圖像才發生這種情況，對於JPG，JPEG和GIF來說，它工作得非常完美。

有人可以幫我嗎？

提前致謝！

例

這是我的代碼：

公共函數create_square_image（$ original_file，$ destination_file = NULL，$ square_size = 100）{

    // get width and height of original image
    $imagedata = getimagesize($original_file);
    $original_width = $imagedata[0];    
    $original_height = $imagedata[1];

    if($original_width > $original_height){
        $new_height = $square_size;
        $new_width = $new_height*($original_width/$original_height);
    }
    if($original_height > $original_width){
        $new_width = $square_size;
        $new_height = $new_width*($original_height/$original_width);
    }
    if($original_height == $original_width){
        $new_width = $square_size;
        $new_height = $square_size;
    }

    $new_width = round($new_width);
    $new_height = round($new_height);

    // load the image
    if(substr_count(strtolower($original_file), ".jpg") or substr_count(strtolower($original_file), ".jpeg")){
        $original_image = imagecreatefromjpeg($original_file);
    }
    if(substr_count(strtolower($original_file), ".gif")){
        $original_image = imagecreatefromgif($original_file);
    }
    if(substr_count(strtolower($original_file), ".png")){


                    $original_image = imagecreatefrompng($original_file);       
    }

    $smaller_image = imagecreatetruecolor($new_width, $new_height);
    $square_image = imagecreatetruecolor($square_size, $square_size);

    imagecopyresampled($smaller_image, $original_image, 0, 0, 0, 0, $new_width, $new_height, $original_width, $original_height);

    if($new_width>$new_height){
        $difference = $new_width-$new_height;
        $half_difference =  round($difference/2);
        imagecopyresampled($square_image, $smaller_image, 0-$half_difference+1, 0, 0, 0, $square_size+$difference, $square_size, $new_width, $new_height);
    }
    if($new_height>$new_width){
        $difference = $new_height-$new_width;
        $half_difference =  round($difference/2);
        imagecopyresampled($square_image, $smaller_image, 0, 0-$half_difference+1, 0, 0, $square_size, $square_size+$difference, $new_width, $new_height);
    }
    if($new_height == $new_width){
        imagecopyresampled($square_image, $smaller_image, 0, 0, 0, 0, $square_size, $square_size, $new_width, $new_height);
    }


    // if no destination file was given then display a png      
    if(!$destination_file){
        imagepng($square_image,NULL,9);
    }

    // save the smaller image FILE if destination file given
    if(substr_count(strtolower($destination_file), ".jpg")){
        imagejpeg($square_image,$destination_file,100);
    }
    if(substr_count(strtolower($destination_file), ".gif")){
        imagegif($square_image,$destination_file);
    }
    if(substr_count(strtolower($destination_file), ".png")){
        imagepng($square_image,$destination_file,9);
    }

    imagedestroy($original_image);
    imagedestroy($smaller_image);
    imagedestroy($square_image);

}

Answer 1

保存時需要使用imagesavealpha()來保留Alpha通道。